1. Field of Invention
The present invention is directed to a bridging apparatus for use with an optical crossconnect device. More particularly, the present invention relates to a bridging apparatus that splits a light beam being inputted into the optical crossconnect device into first and second light beam portions.
2. Description of Related Art
Many telecommunications companies have constructed ground-based telecommunications networks throughout the world. As is commonly known in telecommunications networks art, a plurality of switching stations are interconnected by trunk lines. Occasionally, a trunk line fails as a result of a natural disaster or other event. When a trunk line fails, the communication signals must be rerouted through alternative operating trunk lines.
When a trunk line fails, communications, at least briefly, are interrupted. Upon repair of the failed trunk line, it is often desirable to switch back to the original trunk line after it is repaired. This process, commonly referred to as "restoration," causes yet another, although brief, communications interruption when switching from the alternate trunk line back to the original trunk line. In the communications industry, it is desirable to minimize any interruptions of communications.
Many ground-based communications networks use fiber optic cables. To facilitate switching at the switching stations, optical crossconnect devices are used. A crossconnect device 2 as shown in FIG. 1 represents a conventional crossconnect device that includes a plurality of optical switches 4 that are arranged in a plurality of rows and columns. Each optical switching device 4 includes a reflective panel 6 that moves between a reflective state and a non-reflective state by an actuator 8. For further information regarding crossconnect devices, refer to "An Introduction to Photonic Switching Fabrics" by H. Scott Hinton, published by Plenum Press in New York and an article in the Journal of Microelectromechanical Systems, vol. 5, no. 4, December, 1996, entitled "Electrostatic Micro Torsion Mirrors for an Optical Switch Matrix" by Hiroshi Toshiyoshi and Hiroyuki Fujita. The crossconnect device 2 includes light signal ports 1in-4in and light output ports 1out-4out. By way of example only, a light beam L is emitted from light input port 1in and is reflected from the reflective panel 6 drawn phantomly of an optical switching device 4 located in column C1 and row R2. The light beam L is redirected from its first optical path onto a second optical path to the light output port 2out. A fiber optic cable from an incoming trunk line is connected to the light input ports 1in-4in and fiber optic cables are also connected to the light output ports 1out-4out which are connected to various outgoing trunk lines.
If the outgoing trunk line connected to the light output port 2out fails, it would be desirable to redirect the light beam L to another light output port connected to a different operating trunk line, for example, by using light output port 3out. To switch the light beam L from light output port 2out to light output port 3out, the reflective panel 6 of the optical switching device located in column C1 and row R2 must move to the non-reflective state while the reflective panel 6 in column C1 and row R3 moves to the reflective state.
When the outgoing trunk line connected to the light output port 2out fails or is otherwise rendered inoperative, interruption occurs in the communication. By redirecting the light beam L to the light output port 3out which is connected to a different trunk line than the light output port 2out, communications is now restored. Often, it is desirable to switch back to the original outgoing trunk line once it becomes operative. To switch back from the light output port 3out to the light output port 2out, an interruption again occurs in the communication.
It is desirable in the communication industry to minimize any interruptions during communications. The present invention addresses this concern.